Sound recording



July 7, 1942. c. RUTH 2,289,075

SOUND RECORDING Filed May 26, 1941 2 Sheets-Sheet l l I mrksruzk,

ATTO R N EYS July 7, 1942. c. E. RUTH 2,289,075

SOUND RECORDING Filed May 26, 1941 -2 Sheets-Sheet 2 III lllllu INVEN OR ATTORNEYS Patented 'July 7, 1942 I UNITED STATES PATE NT OFFICE 15 Claims.

My invention relates to the art of recording sound on film, and has among its objects and advantages the provision of an improved sound recording system.'

In the accompanying drawings:

Figure 1 is a perspective view of the system;

Figure 2 is an end view of an electromagnet and tube element employed in the system, with certain parts broken away for the sake of illustration;

Figure 3 is a top plan view of the electromagnet and tube element of Figure 2;

Figure 4 is a view illustrating an apertured plate employed in the system;

Figure 5 is a view illustrating a plate having a differently formed aperture therein;

Figure 6 is a perspective view of a modified form of the sound recording system;

Figure 7 is an end view of the tube unit;

Figure 8 is a side view; and

Figure 9 is a perspective view of a voice coil frame.

In the embodiment selected to illustrate my invention, the electromagnet I0 includes a core I2 of generally U-shaped configuration, as when viewed according to Figs. 1 and 2. with a voice coil I4 mounted on the bight portion of the core. Between the spaced poles I8 and I8 of the coreis positioned a lamp 20, and the lamp is provided with a filament 22 formed to the contour of a U having its legs secured to supporting and terminal elements 24.

An opening 28 of rectangular configuration is provided in the pole I8, and the filament 22 is so positioned as to bring its legs in a plane horizontally aligned centrally of the opening 28. A shield 28 of Audio iron encircles a portion of the leg 38 of the filament 22, but the leg 32 of the filament is exposed and lies between the shield and the pole I8. "Audio iron signifies iron that has very little magnetic retention, but is of high permeability, and will change field direction readily, i. e., as rapidly as audio frequency. Iron such as is employed in the audio frequency transformers of radios is satisfactory. Support for ,the shield is afforded through the medium of two members 34 welded to the shield. A filament support 38 is welded to the shield 28 and has a hooked end 138 engaging the bight of the filament.

In operation, thelamp 20 is located between the poles I8 and I8, so that the direct current carrying filament 22 is located in an alternating magnetic field which is created by the voice coil I4. As the magnetic field alternates, the

filament 22 will vibrate at right angles to the lines of force in the magnetic field. The frequency and amplitude to which the filament will vibrate are determined by the frequency and strength of the alternating magnetic eld, which in turn are determined by the frequency and strength of the current flowing in the voice coil I4. In addition to being located at right angles to the lines of force of the magnetic field, the filament 22 is heated to incandescence and functions as the light source necessary to expose the film upon which the sound track is made.

Light passes through the opening 28 and a lens 4I) to be projected onto the plate 42 having a perforation 44 for the passage of light onto the film 48 moving relatively to the plate in the direction of the arrow 48. The opening 44 is V-shaped at its bottom and the image 50 of the filament is projected across the V contour of the opening 44 to be projected onto the film 48.

As the filament 22 vibrates, the image 50 vibrates'vertically s0 that the length of the segment of the image 5D that falls upon the film 48 varies with the vertical shift of the image. Thus the sound track 52 will take a pattern corresponding to the variable lengths of the segments projected through the opening 44.

The shield 28 functions as a concentrator of the magnetic field and causes the leg 32 of the filament to be located in a strong magnetic field, while the leg 30 has some of its extent passing through the shield to be shielded from the magnetic field. Supporting members 34 are sufciently. sturdy to prevent twisting or misalignment of the shield 28, and the filament support 38 is sufficiently resilient to take up slack in the filament when it expands upon heating.

Fig. 5 illustrates a plate 54 corresponding to the plate 42, in which the plate is provided with a perforation 58, and the edge 58 defining one wall of the perforation is straight but angled with respect to the horizontal so that the filament image 80 is masked at one end by the angular edge and at its other end by the straight edge 82. Thus a sound track contoured by the perforation 58 will be single edged rather than double edged, as in connection with the perforation 44.

In Figs. 6. 7 and 8 I illustrate a different form of invention wherein two voice coils 84 and 88 are located inside the glass tube 88. Voice coil 84 is provided with a core 10, while the opening carried by a terminal support 18 and a support 1l. The iron core 14 tends to concentrate and strengthen the magnetic field in which the lament 14 is located. A bridge 89 is welded to a support 82 and spaces the ltwo voicecoils 84 and 48.

In Fig. 9, bridge 80 is provided with two frame elements 83 and 8l on which the voice coils 84 and 48 are respectively wound, with the core 1D fitting inside the frame element 83. Bridge 80, as well as the frame elements 83 and 85, is made of non-magnetic sheet metal and does not influence the magnetic field. The coils are submitted to` their respective frame elements, and the core 'Il may also besubmitted to the frame element II.

Voice coils 64 and 84 are connected in series, as indicated by the lead 81 in Fig. 6, and the base structure of the tube 88 is provided with voice coil terminals 89 and filament terminals 9|. A lead 93 connects one of the terminals 89 with the voice coil 84, the lead 81 interconnects the two voice coils, and a lead 95 connects the voice coil 80 with the support 82. Accordingly, the

bridge support 82 is an element in the voice coil circuit, this bridge support being electrically connected with the other of the terminals 89. Filament 14 is electrically connected with one of the terminals 9| and the support 18 is electrically connected with the other terminal 9| so that the filament support 12 is an element in the filament circuit. Filament 14 is formed of non-magnetic material.

I'he support 18 is of such resiliency as to absorb slack in the lament 'I4 incident to expansion upon heating.

The filament image 84 is projected through a lens 88 and onto the plate 88 having a perforation 90 corresponding to the perforation 44. The

segment of the image 84 projected through the 94 takes the form of a beam |00 square in cross section, and the width of the beam is varied through the vertical vibration or shift in the lament. The film 98, however, is exposed to a line of light that varies in length in accordance with filament vibration.

In both forms, the filament, which vibrates or oscillates in the magnetic eld, functions as a light source to expose the portion of the film upon which the sound track is made.

Having thus described certain embodiments of my invention in detail, it is, of course, understood that I do not desire to limit the scope thereof to the exact details set forth except insofar as those details may be defined in the appended claims.

I claim:

1. In a sound recording system of the type described, an incandescent vibratory ilament, means for dening the shape of the beam of light from said filament, and a magnetic iield for vibrating said lament in accordance with impulses to be recorded, said incandescent vibratory filament being positioned at right angles to the lines of force of the magnetic field.

2. In a sound recording system of the type described, an incandescent vibratory filament, means for dening the shape of the beam of light from said filament, and a magnetic field for vibrating said filament in accordance with impulses to be recorded, said magnetic field comprising a core having spaced poles and a voice coil mounted thereon, with the incandescent vi-4 bratory filament located between said poles at right angles to the lines of force of the mag netic eld.

3. I n a sound recording system of the type described, an incandescent vibratory lament, means for defining the shape of the beam of light from said filament, and a magnetic iield for vibrating said filament in accordance with impulses to be recorded, said magnetic eld comprising a core having poles and a voice coil mounted on the core, with the incandescent vibratory filament located between said poles at right angles to the lines of force of the magnetic iield, one of said poles having an opening located for the passage of said beam of light therethrough.l

4. In a sound recording system of the type described, an incandescent vibratory filament. means for dening the shape of the beam of light from said lament, a magnetic field for vibrating said filament in accordance with impulses to be recorded, said incandescent vibratory filament being in the nature of a U having its legs lying in the plane of said beam of light, and a shield about the greater extent ci' one of said legs.

5. In a sound recording system of the type described, an incandescent vibratory filament, means for defining the shape of the beam of light from said filament, a magnetic eld for vibrating said filament in accordance with impulses to be recorded, said magnetic field comprising a core having spaced poles and a voice coil mounted on the core, with the incandescent vibratory iilament located between said poles at right angles to the lines of force of the magnetic field, one of said poles being provided with an opening for the passage of said beam of light, and said incandescent vibratory lament being contoured in the nature of a U having the legs thereof lying in the plane of said beam of light.

6. In a sound recording system of the type described, an incandescent vibratory lament, means for dening the shape of the beam of light from said filament, a magnetic iield for vibrating said lament in accordance with impulses to be recorded, said magnetic ileld comprising a core having spaced poles and a voice coil mounted on the core, with the incandescent vibratory iilament located between said poles at right angles to the lines of force of the magnetic ileld, one of said poles being provided with an opening for the passage of said beam of light, said incandescent vibratory filament being contoured in the nature of a U having the legs thereof lying in the plane of said beam of light, and a shield about the greater extent of one of said legs.

7. In a sound recording system of the type described, an incandescent vibratory filament, means for deiining the shape of the beam of light from said filament, a magnetic field for vibrating said filament in accordance with impulses to be recorded, said magnetic ileld comprising a core having spaced poles and a voice coil mounted on the core, with the incandescent vibratory filament located between said poles at right angles to the lines of force of the magnetic iield, one of said poles being provided with an opening for the passage of said beam of light, said incandescent vibratory lament being contoured in the nature of a U having the legs thereof lying in the plane of said beam of light, a shield about the greater extent of one of said legs, and a glass tube enclosing said incandescent vibratory filament and said shield.

8. In a sound recording system of the type described, an incandescent vibratory filament, means fordelining the shape of the beam of light from said lament,'a magnetic eld for vibrating said filament in accordance with impulses to be recorded, said magnetic field comprising a core having spaced poles and a voice coil mounted on the core, with the incandescent vibratory lament located between said poles at right angles to the lines of force of the magnetic field, one of said poles being provided with an opening for the passage of said beam of light, said incandescent vibratory lament being contoured in the nature of a LI having the legs thereof lying in the plane of said beam `of light, a shield about the greater extent of one of said legs, a glass tube enclosing said incandescent vibratory lament and said shield, a support for said shield, and a support for the incandescent vibratory filament engaging the bight thereof and being resilient to aiiord support under expansion and contraction of said incandescent vibratory filament.

9. In a sound recording system of the type described, an incandescent vibratory filament,

means for defining the shape of the beam of light from said filament, a magnetic eld for vibrating said lament in accordance with impulses to be recorded, said magnetic eld comprising two spaced voice coils having said incandescent vibratory filament positioned between the voice coils, one of said voice coils having an opening for the passage of said beam of light, and the other voice coil having a core lying in the plane of said lament and said opening.

10. In a sound recording system of the type described, an incandescent vibratory lament, means for deiining the shape of the beam of light from said lament, a magnetic field for vibrating said lament in accordance with impulses to be recorded, said magnetic field comprising two spaced voice coils having said incandescent vibratory lament positioned between the voice coils, one of said voice coils having an opening for the passage of said beam of light, the other Voice coil having a core lying in the plane of said filament and said opening, a spacing means between said voice coils, a support for said incandescent vibratory filament, and a glass tube enclosing said voice coils, said spacing means, said support, and the incandescent vibratory lament.

11. In a sound recording system oi' the type described, a vibratory light source, means for defining the shape of the beam of light from said source, and means for vibrating said light source in accordance with impulses to be recorded, said first-mentioned means comprising an opening located in the line of said beam of light and contoured to change the pattern of said beam of light through relative movement between the beam of light and the opening.

l2. In a sound recording system oi the type described, a vibratory light source, means for deiining the shape of the beam of light from said source, and means for vibrating said light source in accordance with impulses to be recorded, said first-mentioned means Vcomprising 'an opaque plate having a perforation therein, with said perforation having a portion thereof simulating a V located in line with the beam of light.

13. In a sound recording system of the type described, a vibratory light source, means for deflning the shape of the beam of light from said source, means for vibrating said light source in accordance with impulses to be recorded, said first-mentioned means comprising an opaque plate having a perforation therein, with said perforation having a, portion thereof simulating a V located in line with the beam of light, and a lens means located between said vibratory light source and said plate in line with said beam of light.

14. In a sound recording system of the type described, a vibratory light source, means for defining the shape of the beam of lightl from said source, and means for vibrating said light source in accordance with impulses to be recorded, said inst-mentioned means comprising an opaque plate having a perforation therein, with said perforation so contoured as to fashion a sound track having one straight edge and an irregularly shaped opposite edge.

l5. In a sound recording system of the type described, a vibratory light source, means for defining the shape of the beam of light from said source,` means for vibrating said light source in accordance with impulses to be recorded, said rst-mentioned means comprising a first lens, a plate having a perforation therein, a cylindrical lens, and a plate having a narrow slot, with said first lens, said perforation, said cylindrical lens and said slot aligning with the axis of said beam of light.

CHARLES E. RUTH. 

